Teleconnected warm and cold extremes of North American wintertime temperatures

TL;DR

This paper introduces a new statistical model to analyze teleconnected temperature extremes across North America, capturing opposite-tail dependence patterns linked to atmospheric flow, extending traditional correlation-based teleconnection analysis.

Contribution

It develops a flexible mixture of rotated Archimedean copulas to model opposite-tail dependence in spatial temperature extremes, addressing limitations of existing models.

Findings

Quantifies opposite-tail dependence between Alaska and continental US temperatures.

Links dependence patterns to atmospheric flow regimes.

Extends teleconnection analysis beyond correlation to tail dependence.

Abstract

Current models for spatial extremes are concerned with the joint upper (or lower) tail of the distribution at two or more locations. Such models cannot account for teleconnection patterns of two-meter surface air temperature ($T_{2m}$) in North America, where very low temperatures in the contiguous Unites States (CONUS) may coincide with very high temperatures in Alaska in the wintertime. This dependence between warm and cold extremes motivates the need for a model with opposite-tail dependence in spatial extremes. This work develops a statistical modeling framework which has flexible behavior in all four pairings of high and low extremes at pairs of locations. In particular, we use a mixture of rotations of common Archimedean copulas to capture various combinations of four-corner tail dependence. We study teleconnected $T_{2m}$ extremes using ERA5 reanalysis of daily average two-meter temperature during the boreal winter. The estimated mixture model quantifies the strength of opposite-tail dependence between warm temperatures in Alaska and cold temperatures in the midlatitudes of North America, as well as the reverse pattern. These dependence patterns are shown to correspond to blocked and zonal patterns of mid-tropospheric flow. This analysis extends the classical notion of correlation-based teleconnections to considering dependence in higher quantiles.